PYEONGCHANG, South Korea — When the North Korean leader, Kim Jong-un, decided to send a large delegation to the Winter Olympics in South Korea this month, the world feared he might steal the show.

If that was indeed his intention, he could not have chosen a better emissary than the one he sent: his only sister, Kim Yo-jong, whom news outlets in the South instantly called “North Korea’s Ivanka,” likening her influence to that of Ivanka Trump on her father, President Trump.

Much as Ms. Trump has been when traveling with her father, Ms. Kim was closely followed by the news media during her three-day visit to Seoul and to Pyeongchang, which is hosting the Olympics. She flew back to North Korea on Sunday night.

Flashing a sphinx-like smile and without ever speaking in public, Ms. Kim managed to outflank Mr. Trump’s envoy to the Olympics, Vice President Mike Pence, in the game of diplomatic image-making.

While Mr. Pence came with an old message — that the United States would continue to ratchet up “maximum sanctions” until the North dismantled its nuclear arsenal — Ms. Kim delivered messages of reconciliation as well as an unexpected invitation from her brother to the South Korean president, Moon Jae-in, to visit Pyongyang, the North Korean capital.

Ms. Kim attracted attention wherever she turned up — at the opening ceremony, in the stands at the Olympic debut of the unified Korean women’s ice hockey team, and at a performance in Seoul by a North Korean art troupe.

Only the media would make the US out like the bad guys and North Korea like happy-go-lucky super models.